1. Field of the Invention
The present invention relates to controlling point-of-load regulators, and more particularly, to a system and method using an analog bus to communicate with point-of-load regulators.
2. Related Art
Point-of-load (“POL”) regulators, which are also referred to as voltage regulators or DC/DC converters, are commonly used in conjunction with electronic circuits, typically to satisfy voltage/current requirements of the electronic circuits that differ from the voltage that is readily available or the current that can practically be delivered. For example, some electronic devices only include a single voltage input (e.g., 12 v), but require different voltages for circuits contained within (e.g., 1.2 v, 3.3 v, 5 v, etc.). A common solution is to design multiple POL regulators within the device for converting the single input voltage into multiple voltage levels internally.
As another example, some electronic devices include circuits that require low voltage (e.g., 1 v), high current (e.g., 100 A) power supplies. This is problematic in that it is impractical to deliver high current at low voltages over a relatively long distance and still meet desired regulation performance. A common solution is to use a high voltage, low current power supply and design a POL regulator near the internal circuit. This allows low current to travel throughout the device, and provides a low voltage, high current power supply (i.e., using the POL regulator) near the internal circuit.
Traditionally, a plurality of POL regulators will operate in conjunction with a supervisory power supply controller (“controller,” “manager” or “master”) that digitally activates, programs, and monitors the POL regulators. Specifically, the controller uses a multi-connection serial or parallel bus (e.g., a six bit parallel bus) to activate and program each POL regulator. Such a parallel bus may include an enable/disable bit for turning the regulator on and off and VID code bits for programming the output voltage or current set-point of the regulator and other bits for sequencing. The controller further uses additional connections (e.g., two or three wires) to monitor the voltage/current that is being delivered by each regulator, the ambient temperature, and other factors.
A drawback with such control systems is that they add complexity and size to the overall electronic device by using, for example, a six bit parallel bus to operate each POL regulator and three additional wires to monitor each POL regulator. In other words, a controller operating in accordance with this control system may utilize twenty-seven connections (i.e., twenty-seven wires or traces) in order to communicate with three POL regulators.
Another issue with the digital bus is that it requires multiple D/A and A/D conversion stages, which are expensive and also introduce delay. Further, it provides only imprecise control and monitoring of the POL regulator's functions and parameters. The least significant bit on a 6-bit digital bus may affect the output voltage set point as much as 50 mV or 5% of a 1V output, for example. Using more bits will solve the resolution problem at the expense of rapidly increased complexity and cost. It also requires duplicated internal components for precision voltage reference, A/D, sequencing and DSP in each POL regulator, which increases their cost for systems with multiple POLs.
On the other hand, digital serial communication of non-critical data and control signals can be highly effective and economical.
It would be advantageous to have a system and method for communicating with POL regulators that overcomes these drawbacks.
More particularly, it would be desirable to achieve the benefits of the digital platforms, such as programmability and communications, which may include the use of proprietary techniques and/or known techniques such as I2C. It would also be desirable to use suitable existing technologies, such as IC design and fabrication techniques and components such as EEPROM's and the existing precise and reliable analog PWM technology.